Electric switch having contacts convertible between normally open and normally closed conditions



1, 1965 J. E. KEYSER ETAL 3,204,068

ELECTRIC SWITCH HAVING CONTACTS CONVERTIBLE BETWEEN NORMALLY OPEN AND NORMALLY CLOSED CONDITIONS Filed Nov. 8, 1962 INVENTORS. JOHN E KEYSER, Roy E. WHEELER BY M ATTORNEY.

United States Patent 3,204,068 ELECTRIC SWITCH HAVHNG CONTACTS CON- VERTKBLE BETWEEN NURMALLY OPEN AND NDRMALLY CLOSED CONDITIGNS John E. Keyser, llloomingtou, and Roy E. Wheeler,

Champaign, Ill., assignors to General Electric Company, a corporation of New York Filed Nov. 8, 1962, Ser. No. 236,255 7 Claims. (Cl. 200-159) This invention relates to electric switches and has particular relation to switches of the push button type.

Push button switches of previous design have assumed a wide variety of forms and generally include a reciprocable contact carrier mounting a movable contact which is reciprocable relative to a plurality of fixed contacts. Switches of this type should desirably be of inexpensive compact construction with a minimum number of parts. Also, in many installations it is desirable that provision be made for permitting rapid installation and removal of the movable contact relative to the contact carrier.

Certain switch installations require that the switch be convertible between normally open and normally closed contact conditions and it is desirable that provision be made for permit-ting suchconversion to be rapidly performed with a minimum eifort and with a minimum manipulation of parts of the switch. Many installations require the provision of a multiple button push switch for cont-rolling a plurality of electric circuits. As one example, a two button, start-stop push switch is generally employed in connection with magnetic motor starters for controlling two electric circuits. In such applications it is desirable that the switch be designed so as to permit the ready repositioning of the fixed contacts relative to the movable contacts to modify the circuit connections as desired. Although switches of previous design have incorporated one or more of the above desirable features, such switches have not been entirely satisfactory due to their bulky, multipart construction necessitating the performance of cumbersome and time consuming operations to effect the contact conversions and repositionings abovereferred to.

It is therefore an object of the present invention to provide a novel and improved electric switch which is of compact and inexpensive construction employing a minimum number of parts.

it is another object of the invention to provide a novel and improved electric switch having a movable contact carrier which detachably mounts a movable contact in a manner permitting rapid installation and removal of the movable contact relative to the carrier.

It is a further object of the invention to provide a novel and improved electric switch having a movable contact carrier with provision for detachably mounting a movable contact in a selected one of a plurality of different positions to permit conversion of the switch between normally open and normally closed contact conditions with a minimum manipulation of parts.

It is still another object of the invention to provide a novel and improved electric push button switch having a movable contact carrier mounted by a housing for reciprocation relative to a plurality of fixed contacts which are detachably mounted by the housing for rapid installation and removal relative thereto and which can be readily repositioned relative to the housing to provide different circuit arrangements controllable by movement of the carrier.

In carrying out the invention in one form an electric push button switch is provided including an insulating base having a pair of spaced parallel openings which receive respectively a pair of reciprocable push buttons each having a stem formed with a pair of axially spaced pas- 3,204,063 Patented Aug. 31, 1965 "Ice sages for selectively detachably receiving a movable contact in the form of an electroconductive rod. The stem of each contact carrier is axially split through each of the two associated passages and each passage includes a side wall formed with ribs which are received by snap engagement in annular grooves formed intermediate the ends of the movable contact rods. The base detachably mounts a plurality of identically configured fixed contacts which are located in a common plane. The base is designed so that the fixed contacts may be arranged to provide a pair of isolated circuits controllable by the movable contact rods or a pair of circuits having a common conductor controllable by the contact rods.

The arrangement is such as to permit rapid conversion between normally open and normally closed contact conditions. Each push button is normally urged outwardly of .the base by resilient biasing means and is moved inwardly thereof in response to depression of the push button. When the contact rod of an associated push button is in the mounting passage which is adjacent the free end of the stem, a normally closed contact condition is established, and when the contact rod is repositioned within the other mounting passage more remote from the stem end, the switch is converted to a normally open contact condition.

Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a fragmentary view in elevation of a two butt-on push button switch constructed according to the present invention and mounted on a supporting panel;

FIG. 2 is a view in elevation of the switch mounting base showing in particular the arrangement of the fixed contacts for providing control of two independent circuits;

FIG. 3 is a view in section taken along the line 33 of FIG. 1;

FIG. 4 is a view in section taken along the line 4-4 of FIG. 2;

FIG. 5 is a view in elevation of the cover which is detachably mounted .to the mounting base;

FIG. 6 is a view similar to FIG. 2 showing the fixed contacts arranged in a manner ditferent than their arrangement in FIG. 2 for providing two electric circuits having a common conductor controllable by the movable contact carrier; and

FIG. 7 is an enlarged fragmentary view in end elevation of the movable contact carrier.

Referring now to the drawings, there is illustrated in FIG. 1 a push button station 10 including an electric switch constructed in accordance with the present invention. The switch includes an insulating supporting base 11 and a cover 12 detachably secured to the base, and is mounted upon a supporting panel 13. In FIG. 1 the switch is illustrated as a two button, start-stop switch which is suitable for use in association with magnetic motor starters. As will presently appear, however, the invention is applicable to switches having single push buttons as well as switches including multiple push but tons.

In general, the switch illustrated includes a pair of reciprocable contact carriers 14 and 15 formed of suitable insulating material which detachably mount respectively electroconductive contacts 16 and 17 reciprocable relative to a plurality of fixed electroconductive contacts 1821 detachably mounted on the base 11. As will appear hereinafter, the present invention provides that the base 11 and the fixed contacts 18-21 are configured so that the fixed contacts can be readily installed and removed relative to the base and can be repositioned to present various circuit configurations to the movable contacts. The invention also provides contact carriers and movable contracts which are arranged so that the mov able contacts can be selectively positioned at different locations on the contact carriers to permit rapid conversion between normally open and normally closed contact conditions.

More specifically, the base 11 is formed with a pair of spaced generally parallel extending openings which receive the reciprocable contact carriers 14 and 15 as best shown in FIG. 4. The opening for the carrier 14 includes an enlarged upper section opening at the top of the base 11 as viewed in FIG. 4, and a restricted section 26 communicating with the section 25 and opening at the lower side of the base. In a similar manner, the opening for the contact carrier 15 includes an enlarged upper section 27 communicating with a restricted lower section 28. The contact carrier 14 includes an enlarged head 30 and a restricted stem 31 respectively positioned in the enlarged opening 25 and the restricted opening 26. Similarly, the carrier 15 includes an enlarged head 32 located within the opening 27 and a stem 33 extending therefrom through the opening 28. The enlarged heads 30 and 32 of the contact carriers consist of legend caps 36 which are snap fit on head-s 37 of the stems 31 and 33 (FIG. 3). The stems 31 and 33 of the contact carriers project beyond the lower surface of the base 11 into cavities 34 and formed in the cover section 12.

In order to urge the contact carriers 14 and 15 to their normally extended positions as shown in FIG.,4, resilient means are provided in the form of a pair of helical springs 40 and 41 respectively positioned in the enlarged openings 25 and 27 to bear against the undersides of the enlarged head sections 30 and 32 and against the bottom walls of the openings 25 and 27. The contact carriers 14 and 15 are reciprocable between the extended position shown in FIG. 4 and depressed positions wherein the head sections 30 and 32 are moved further into the openings 25 and 27 to compress the associated springs 40 and 41.

In accord with the present invention, provision is made for selectively mounting the movable contacts 16 and 17 in either one of two axially spaced positions on the associated contact carriers to permit conversion between normally open and normally closed contact conditions. For this purpose each of the contact carriers is provided with a pair of axially spaced passages for detachably mounting its movable contact. As best shown in FIG. 4, the stem 31 of the carrier 14 is provided with a pair of axially spaced passages 42 and 43 extending entirely through the stem generally perpendicular to the stern axis. In a similar manner the stem 33 of carrier 15 is provided with a pair of axially spaced passages 44 and 45 extending entirely therethrough perpendicular to the stem axis. To facilitate mounting of the movable contacts in the passages the stems 31 and 33 are axially split through the associated passages as shown by the axially extending slots 46 and 47 which permit limited lateral relative displacement between the resulting half sections of the carrier stems.

According to the present invention the movable contacts 16 and 17 are in the form of straight cylindrical wires or rods of substantially uniform cross section throughout their lengths. The contact rods 16 and 17 are detachably held within selected ones of the passages 42-45 by means of internal ribs 50 (FIG. 7) formed on the side walls of the passages and which fit with snap engagement into peripheral grooves 51 formed intermediate the ends of the contact rods 16 and 17. The slots 46 and 47 in the stems 31 and 33 facilitate installation and removal of the contacts 16 and 17 relative to the several passages 42-45 and the contacts are firmly held within the passages by the cooperating ribs and grooves 50 and 51.

In order to guide the movable contacts 16 and 17 for movement during reciprocation of the carriers 14 and 15 a plurality of guide slots are formed in the base 11 and in the cover 12 which contain the stems of the contact carriers and the movable contacts to prevent rotation of the contact carriers during reciprocation thereof. For this purpose the wall of the restricted opening 26 is interrupted by a pair of diametrically opposed slots 52 whereas the wall of opening 28 is interrupted by a pair of diametrically opposed slots 53. The slots 52 and 53 are configured to receive the contacts 16 and 17 when such contacts are located on the stems in a manner to establish normally open contact conditions as will presently appear. The slots 52 and 53 also are disposed at predetermined angles with respect to each other as best shown in FIG. 2 for a purpose appearing hereinafter. When the contacts 16 and 17 are in positions to establish normally open contact conditions, the contact 16 in FIG. 4 being so positioned, the contacts rest against the bottom wall of the associated slots 52 to thereby hold the carriers in operative positions on the base. The side walls of the restricted openings 26 and 28 are also formed with diametrically opposed slot-s 55 and 56 as best shown in FIG. 2 which extend generally perpendicular to the slots 52 and 53 for receiving oppositely disposed ribs 57 and 58 respectively formed on the stems 31 and 33 of the contact carriers. The contact carriers are thus mounted in the desired angular positions and are prevented from turning about their axes during reciprocation thereof.

The fixed contacts 18-21 are of substantially identical construction being of generally planar configuration and including respectively pairs of spaced contact parts or legs 60-63 in the general plane thereof. The fixed contacts are detachably mounted on the base adjacent the open ends of the restricted openings 26 and 28. In the embodiment of FIG. 2 four fixed contacts are illustrated with two fixed contacts being associated With each of the contact carriers. The spaced legs of the contacts of each pair extend toward each other and one leg of each contact of each pair overlies the associated one of the slots 52 and 53 for engagement with the associated movable contacts 16 and 17. As best shown in FIG. 4 the contact parts or legs 60 and 61 of the fixed contacts 18 and 19 lie in a common plane which is between the passages 42 and 43. The common plane including the contact parts or legs 62 and 63 of the fixed contacts 20 and 21 is similarly disposed between the passages 44 and 45. In order to detachably mount the fixed contacts 18-21 on the base 11, the fixed contacts include respectively pairs of spaced parallel-extending projections 70-73 which extend away from the observer as viewed in FIG. 2 into pairs of slots 74-77 formed in the base 11 and extending generally parallel to the axes of the stems 31 and 33 of the contact carriers. The slots 74-77 are configured to receive the projections 70-73 of the fixed contacts with a slight press fit thereby permitting ready installation and removal of the fixed contacts relative to the base 11. Such installation and removal is facilitated by the provision of pairs of upstanding projections -83 on the fixed contacts which extend in directions opposite to the directions of extension of the projections 70-73. The projections 80-83 provide grips for an operator to permit installation and removal of the fixed contacts. In addition, one of the projections 80-83 of each of the fixed contacts is received in a separate one of a plurality of slots -88 formed in side walls 89 and 90 of the cover section 12 when the cover section is mounted on the base 11. This arrangement assists in holding the fixed contacts in operative positions on the base.

The fixed contacts 18-21 include threaded openings for threadably receiving terminal screws 91 which extend into openings 92 formed in the base 11 beneath the fixed contacts. The base 11 is formed with two sets of semicircular openings 93 in the end Walls thereof which cooperate with similar openings 94 formed in the cover 12 to provide, when the cover is attached, conductor openings through which extend the conductors secured to the fixed contacts by means of the screws 91. The base 11 and cover 12 are detachably secured by means of a single screw 95 which extends through an opening 96 of the cover into threaded engagement with a threaded opening 97 formed in the base. The switch is attached to the supporting member 13 by means of screws 98 which extend through openings in the member 13 into threaded engagement with openings in the base.

As previously stated, the device of FIG. 2 is shown as including two pairs of fixed contacts for providing two separate circuits controllable by the two contact carriers 14- and 15. The device of FIG. 2 may readily be converted for control of two circuits including a common conductor by removing the fixed contacts 18 and 20 from the base and by inserting a similar fixed contact 99 in the base in the space between the areas previously occupied by the contacts 18 and 20. This arrangement is shown in FIG. 6 wherein the contact Q9 serves as a common contact engageable by both of the movable contacts 16 and 17. The contacts 16 and 17 are oriented such that the ends of each of these contacts lie on opposite sides of the horizontally extending central plane of the device, the contact ends below such plane as viewed in FIGS. 2 and 6 being closer to each other than the contact ends above such plane. This arrangement permits engagement of the contacts 16 and 17 with the adjacent legs 60 and 62 of the fixed contacts 18 and 20 as in FIG. 2, and with the legs of the contact 9 in FIG. 6.

In FIGS. 2 and 4 the contact 16 is shown retained in the passage 42 spaced from the fixed contacts 18 and 19 when the carrier 14 is in its normally extended position to establish a normally open contact condition. To convert to a normally closed contact condition it is only necessary to remove the contacts 18 and 19 from the base, depress the carrier 14 to its full extent, remove the contact 16 from the passage 42 and insert it in the passage 43, release the carrier 14 and install the contacts 18 and 19 on the base. The contact 16 then normally engages the contacts 18 and 19 at the lower surfaces thereof as viewed in FIG. 4, and is moved out of engagement with these contacts in response to depression of the carrier. The contact 17 in FIGS. 2-4 is shown in its normally closed condition and is converted to a normally open condition by depressing the carrier which permits removal of the fixed contacts 20 and 21 from the base and removal of the contact 17 from the passage 45. The contact 17 is then inserted in the passage 44 and the plunger 15 released. Finally, the fixed contacts 20 and 21 are inserted in the base. The carriers 14 and 15 are readily removed from the base by merely removing the contacts 16 and 17 from the stems which releases the carriers 14 and 15 for detachment from the base by movement thereof upwardly as viewed in FIG. 4. It is noted that the conversions are effected without repositioning the fixed contacts and that the common plane of the fixed contact parts has the same axial position for either selected position of each movable contact rod.

While we have shown and described particular embodiments of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects and we, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric switch, a base formed of insulating material and having an opening extending entirely therethrough between its opposite sides, a contact carrier on said base reciprocable relative to said base between extended and depressed positions, said contact carrier having an actuating part on one side of said base and having a stem attached to the actuating part and extending through said opening with the :free end of the stem on the other side of said base, resilient means acting between 6 said base and said contact carrier urging the contact carrier to an extended position, a pair of spaced fixed contacts detachably mounted on said other side of said base, said fixed contacts being of generally planar configuration each having a contact part in the general plane thereof, the stem of said movable contact carrier having a pair of axially spaced passages extending entirely therethrough generally perpendicular to the stem axis, and a movable contact comprising an electroconductive rod detachably received within a selected one of said passages with the ends of said rod projecting externally of the selected passage, said rod when in the passage nearer the stem free end normally engaging the contact parts of said fixed contacts when said contact carrier is extended and being moved out of engagement with the contact parts of said fixed contacts in response to depression of said contact carrier, said rod when in the passage remote from the stem free end normally being spaced from the contact parts of said fixed contacts when said contact carrier is extended and being moved into engagement with the contact parts of said fixed contacts in response to depression of said contact carrier said fixed contact parts being in a common plane which extends parallel to and lies between said axially spaced passages and which has the same axial position for either selected position of said rod.

2. In an electric switch, a base formed of insulating material and having an opening extending entirely therethrough between its opposite sides, a reciprocable contact carrier having an actuating part on one side of the base and having a stern attached to the actuating part extending through said opening to the other side of said base, resilient means acting between said base and said contact carrier urging the contact carrier to an extended position, a pair of fixed contacts detachably mounted on said other side of said base, said fixed contacts being of generally planar configuration each having a contact part in the general plane thereof, said stern having a pair of axially spaced passages extending entirely therethrough generally perpendicular to the stem axis, a movable contact comprising an electroconductive rod detachably received in a selected one of said passages, said opening having a side wall interrupted by diametrically opposed slots proportioned to receive the ends of said rod, said slots opening at said other side of said base and having bottom walls which close the slots to said one side of said base, the contact part of each of said fixed contacts extending over the open end of a separate one of said slots, said rod when in the passage nearer the end of the stem normally being positioned externally of said slots in engagement with said fixed contact parts when said cont act carrier is extended and being moved out of engagement with said fixed contact parts in response to depression of said contact carrier, said rod when in the passage nearer the actuating part of said contact carrier normally being positioned within said slots against the bottom walls thereof spaced from said fixed contact parts when said contact carrier is extended and being moved away from said bottom walls into engagement with said fixed contact parts in response to depression of said contact carrier, said fixed contact parts being in a common plane which extends parallel to and lies between said axially spaced passages and which has the same axial position for either selected position of said rod.

3. A switch as defined in claim 2 wherein said stem is split axially through both of said passages, each of said passages having a side wall formed with opposed ribs, said rod having a peripheral groove intermediate its ends inter-fitting with the ribs of a selected one of said passages.

4. In an electric switch, a base formed of insulating material and including two spaced parallel openings extending entirely therethrough, a pair of reciprocable contact carriers each having an actuatable part on one side of said base and having a stem attached to said actuatable part extending through a separate one of said openings to the other side of said base, a pair of resilient means acting between said base and said contact carriers urging the contact carriers to extended positions, a plurality of fixed contacts detachably mounted on said other side of said base with the fixed contacts being of generally identical planar configuration and lying in a common plane generally perpendicular to the axes of said openings, each fixed contact having a contact part in the general plane thereof, the stems of said contact carriers each containing two axially spaced passages extending entirely therethrough perpendicular to the stem axis, and a pair of movable contacts each on a separate one of said contact carriers for cooperation with a pair of said fixed contacts, each movable contact comprising an electroconductive rod detachably received in a selected one of the two passages of the associated contact carrier, each rod when in the passage nearer the free end of its associated stem normally engaging the associated fixed contact parts when the associated contact carrier is in extended position and being moved out of engagement with the associated fixed contact parts in response to depression of the associated contact carrier, each rod when in the passage nearer the actuatable part of its contact carrier normally being spaced from the associated fixed contact parts when the associated contact carrier is extended and being moved into engagement with the associated fixed contact parts in response to depression of the associated contact carrier, each of said rods being positioned with its ends on opposite sides of a plane which includes the central axes of said parallel openings, the ends of said rods on one side of said plane being closer to each other than the ends of the rods on the other side of said plane, the common plane of said fixed contact parts lying between the axially spaced passages of said stems and having the same axial position for either selected position of each rod.

5. A switch as defined in claim 4 wherein said plurality of fixed contacts comprises four contacts arranged two each at a separate side of said plane.

6. A switch as defined in claim 4 wherein said plurality of fixed contacts comprises three contacts arranged two on said other side of said plane and one on said one side of said plane.

7. In an electric switch, a base formed of insulating material and having a pair of spaced parallel openings extending entirely therethrough, each of said openings having an enlarged section at one side of said base communicating with a smaller section which extends to the other side of said base, a pair of reciprocable contact carriers each having an enlarged actuatable part in a separate one of said enlarged sections and each having a stem connected to the actuatable part and extending through a separate one of said smaller sections, a pair of coil springs each within a separate one of said enlarged sections in engagement with the associated actuatable part urging the contact carriers to extended positions, a plu- 5 rality of fixed contacts detachably mounted on said other side of said base with the fixed contactsbeing of generally identical planar configuration and lying in a common plane generally perpendicular to the axes of said openings, each fixed contact having a contact part in the general plane thereof, each of said stems having a pair of axially spaced passages extending entirely therethrough perpendicular to the stem axis, a pair of movable contacts each on a separate contact carrier comprising a pair of electroconductive rods each detachably positioned within a selected one of the two passages in the associated stem, each of said smaller sections having a side Wall interrupted by two diametrically opposed slots proportioned to receive the ends of the associated rod, each pair of slots opening at said other side of said base and having bottom walls closing the slots to said one side of said base, the contact parts of said fixed contacts extending across the open ends of said slots, each of said rods when in the passage nearer the free end of its associated stem being positioned externally of its associated slots normally in engagement with the contact parts of the associated fixed contacts when the associated contact carrier is in extended position and being moved out of engagement with said contact parts in response to depression of the associated contact carrier, each of said rods when in the passage nearer the actuatable part of the associated contact carrier being positioned within said slots against the bottom walls thereof out of engagement with said contact parts and being moved into engagement with said contact parts in response to depression of the associated contact carrier, the common plane of said fixed contact parts lying between the axially spaced passages of said stems and having the same axial position for either selected position of each rod.

References Cited by the Examiner UNITED STATES PATENTS 2,065,904 12/36 Meuer 200--159 2,106,581 1/38 Unwin 200 166 2,713,092 7/55 Rucks 6t al 200 159 2,738,482 3/56 Benander 200-166 2,924,685 2/60 Burch 200-166 FOREIGN PATENTS 73,430 7/60 France.

KATHLEEN H. CLAFFY, Primary Examiner.

BERNARD A. GILHEANY, ROBERT K. SCHAEFER,

Examiners. 

1. IN AN ELECTIC SWITCH, A BASE FORMED OF INSULATING MATERIAL AND HAVING AN OPENING EXTENDING ENTIRELY THERETHROUGH BETWEEN ITS OPPOSITE SIDES, A CONTACT CARRIER ON SAID BASE RECIPROCABLE RELATIVE TO SAID BASE BETWEEN EXTENDED AND DEPRESSED POSITIONS, SAID CONTACT BARRIER HAVING AN ACTUATING PART ON ONE SIDE OF SAID BASE AND HAVING A STEM ATTACHED TO THE ACTUATING PART AND EXTENDING THROUGH SAID OPENING WITH THE FREE END OF THE STEM ON THE OTHER SIDE OF SAID BASE, RESILIENT MEANS ACTING BETWEEN SAID BASE AND SAID CONTACT CARRIER URGING THE CONTACT CARRIER TO AN EXPANDED POSITION, A PAIR OF SPACED FIXED CONTACTS DETACHABLY MOUNTED ON SAID OTHER SIDE OF SAID BASE, SAID FIXED CONTACT BEING OF GENERALLY PLANAR CONFIGURATION EACH HAVING A CONTACT PART IN THE GENERAL PLANE THEREOF, THE STEM OF SAID MOVABLE CONTACT CARRIER HAVING A PAIR OF AXIALLY SPACED PASSAGES EXTENDING ENTIRELY THERETHROUGH GENERALLY PERPENDICULAR TO THE STEM AXIS, AND A MOVABLE CONTACT COMPRISING AN ELECTROCONDUCTIVE ROD DETACHABLY RECEIVED WITHIN A SELECTED ONE OF SAID PASSAGES WITH THE ENDS OF SAID ROD PROJECTING EXTERNALLY OF THE SELECTED PASSAGE, SAID ROD WHEN IN THE PASSAGE NEARER THE STEM FREE END NORMALLY ENGAGING THE CONTACT PARTS OF SAID FIXED CONTACTS WHEN SAID CONTACT CARRIER IS EXTENDED AND BEING MOVED OUT OF ENGAGEMENT WITH THE CONTACT PARTS OF SAID FIXED CONTACTS IN RESPONSE TO DEPRESSION OF SAID CONTACT CARRIER, SAID ROD WHEN IN THE PASSAGE REMOTE FROM THE STEM FREE END NORMALLY BEING SPACED FROM THE CONTACT PARTS OF FIXED END NORMALLY BEING SPACED FROM THE CONTACT EXTENDED AND BEING MOVED INTO ENGAGEMENT WITH THE CONTACT PARTS OF SAID FIXED CONTACTS IN RESPONSE TO DEPRESSION OF SAID CONTACT CARRIER FIXED CONTACTS PARTS BEING IN A COMMON PLANE WHICH EXTENDCS PARALLEL TO AND LIES BETWEEN SAID AXIALLY SPACED PASSAGES AND WHICH HAS THE SAME AXIAL POSITION FOR EITHER SELECTED POSITION OF SAID ROD. 